The overall aim of this project is to translate new knowledge of fundamental mechanisms of mutagenesis into a clinically useful regimen to reduce the incidence of cigarette smoke-induced lung cancer. Mutations in DNA are generally considered to have an etiologic role in the development of cancer. In the case of non-small cell lung cancers, multiple mutagenic events in alveolar epithelial cells are thought to be causally involved in carcinogenesis. If so, it follows that reducing the frequency of such mutations will reduce the incidence of lung cancer induced by mutagens. Recent data indicates that virtually all mutations induced by the active metabolite of 1 of the principal chemical carcinogens in cigarette smoke, benzo[a]pyrene, are dependent on a newly-described Y-family DNA polymerase encoded by the REV1 gene. This application proposes to reduce the REV1 mRNA in the lungs of mice by intracellular expression of gene-specific ribozymes that are targeted to specific subcellular compartments. Then, the mice will be exposed to an established carcinogen-induced lung cancer protocol. This will be accomplished in 2 Specific Aims: 1) to optimize the aerosolized delivery of a reporter gene to mouse lungs in vivo. 2) to use this method to deliver DNA that expresses ribozymes targeted against REV1 mRNA . The mice and the appropriate controls will be exposed to ongoing protocols that are known to induce lung cancer. The hypothesis predicts that reducing the level of this protein will reduce the mutagenic response of lung epithelial cells to chemical carcinogens in cigarette smoke, and will result in a greatly reduced incidence of lung cancer. This pilot study is designed to provide the experimental rationale to expand the approach to larger protocols in which lung tumors are induced in rodents by cigarette smoke. In principle, the idea of reducing mutagenesis without altering cytotoxic responses presents a novel and attractive method to reduce the risk of lung cancer in smoke-exposed populations prior to the appearance of disease symptoms. [unreadable] [unreadable] [unreadable]